The present disclosure relates to thermoplastic polyolefin (“TPO”) compositions that provide a gloss finish to thermoformed articles.
The use of TPOs in thermoforming applications is known. The thermoforming process typically includes heating a film or a sheet of an extruded TPO at or above the softening temperature of the TPO. The softened sheet is fit along the contours of a mold with pressure supplied from vacuum, air pressure, and/or mechanical draw. The mold is used to form a molded article. Match mold thermoforming places the softened sheet between two cooperating molds. The formed article is cooled, removed from the mold, and trimmed as necessary.
In a typical thermoforming operation, up to as much as 60% of the original TPO sheet is lost as scrap. Attempts to recycle and incorporate scrap into thermoplastic polyolefins have been problematic. This is particularly the case with TPO sheets capped with a gloss layer. The presence of the gloss layer in the scrap lowers the melt strength of the scrap-containing thermoformed sheet. Scrap-containing TPOs also experience an increase in the sag rate during heating of the sheet. This deleteriously impacts the thermoforming operation, causing operability problems and product degradation.
The inability to utilize this high degree of scrap from capped TPO sheets is inefficient and expensive. Desirable would be a thermoplastic polyolefin having a gloss layer that does not negatively impact the thermoforming process or product quality when scrap material of the thermoplastic polyolefin is added to a subsequent thermoplastic composition.